/*
 * Copyright (C) 2007 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.dx.dex.file;

/**
 * An item in a Dalvik file which is referenced by index.
 */
public abstract class IndexedItem extends Item {

	/**
	 * {@code >= -1;} assigned index of the item, or {@code -1} if not yet
	 * assigned
	 */
	private int index;

	/**
	 * Constructs an instance. The index is initially unassigned.
	 */
	public IndexedItem() {
		index = -1;
	}

	/**
	 * Gets whether or not this instance has been assigned an index.
	 * 
	 * @return {@code true} iff this instance has been assigned an index
	 */
	public final boolean hasIndex() {
		return (index >= 0);
	}

	/**
	 * Gets the item index.
	 * 
	 * @return {@code >= 0;} the index
	 * @throws RuntimeException
	 *             thrown if the item index is not yet assigned
	 */
	public final int getIndex() {
		if (index < 0) {
			throw new RuntimeException("index not yet set");
		}

		return index;
	}

	/**
	 * Sets the item index. This method may only ever be called once per
	 * instance, and this will throw a {@code RuntimeException} if called a
	 * second (or subsequent) time.
	 * 
	 * @param index
	 *            {@code >= 0;} the item index
	 */
	public final void setIndex(int index) {
		if (this.index != -1) {
			throw new RuntimeException("index already set");
		}

		this.index = index;
	}

	/**
	 * Gets the index of this item as a string, suitable for including in
	 * annotations.
	 * 
	 * @return {@code non-null;} the index string
	 */
	public final String indexString() {
		return '[' + Integer.toHexString(index) + ']';
	}
}
